Commit 96ec67a7 authored by Przemysław Suliga's avatar Przemysław Suliga Committed by Tim Graham
Browse files

Fixed #26332 -- Fixed a race condition in BaseCache.get_or_set().

parent b4250ea0

django/core/cache/backends/base.py

+5 −5
Original line number Diff line number Diff line
@@ -154,8 +154,7 @@ class BaseCache(object): 
        also be any callable. If timeout is given, that timeout will be used

        for the key; otherwise the default cache timeout will be used.



        Returns the value of the key stored or retrieved on success,

        False on error.

        Return the value of the key stored or retrieved.

        """

        if default is None:

            raise ValueError('You need to specify a value.')
@@ -163,9 +162,10 @@ class BaseCache(object): 
        if val is None:

            if callable(default):

                default = default()

            val = self.add(key, default, timeout=timeout, version=version)

            if val:

                return self.get(key, default, version)

            self.add(key, default, timeout=timeout, version=version)

            # Fetch the value again to avoid a race condition if another caller

            # added a value between the first get() and the add() above.

            return self.get(key, default, version=version)

        return val



    def has_key(self, key, version=None):

docs/releases/1.9.5.txt

+4 −0
Original line number Diff line number Diff line
@@ -12,3 +12,7 @@ Bugfixes 
* Made ``MultiPartParser`` ignore filenames that normalize to an empty string

  to fix crash in ``MemoryFileUploadHandler`` on specially crafted user input

  (:ticket:`26325`).



* Fixed a race condition in ``BaseCache.get_or_set()`` (:ticket:`26332`). It

  now returns the ``default`` value instead of ``False`` if there's an error

  when trying to add the value to the cache.

tests/cache/tests.py

+8 −1
Original line number Diff line number Diff line
@@ -30,7 +30,7 @@ from django.template import engines 
from django.template.context_processors import csrf

from django.template.response import TemplateResponse

from django.test import (

    RequestFactory, SimpleTestCase, TestCase, TransactionTestCase,

    RequestFactory, SimpleTestCase, TestCase, TransactionTestCase, mock,

    override_settings,

)

from django.test.signals import setting_changed
@@ -931,6 +931,13 @@ class BaseCacheTests(object): 
        self.assertEqual(cache.get_or_set('brian', 1979, version=2), 1979)

        self.assertIsNone(cache.get('brian', version=3))



    def test_get_or_set_racing(self):

        with mock.patch('%s.%s' % (settings.CACHES['default']['BACKEND'], 'add')) as cache_add:

            # Simulate cache.add() failing to add a value. In that case, the

            # default value should be returned.

            cache_add.return_value = False

            self.assertEqual(cache.get_or_set('key', 'default'), 'default')





@override_settings(CACHES=caches_setting_for_tests(

    BACKEND='django.core.cache.backends.db.DatabaseCache',